DeCandido was born in New York City to parents who were both fans of Star Trek. He attended Fordham University in the city. He has written tie-ins to numerous other science fiction franchises including Doctor Who, Andromeda, Farscape, X-Men, Spider Man, and Buffy the Vampire Slayer, as well as CSI and Dungeons and Dragons. He has also co-written work with John Gregory Betancourt.